Multi-phase motor drives, including induction motors and permanent magnet motors, are used in a wide variety of applications, due to their inherent redundancy and high reliability. Multi-phase motors offer fault-tolerant operation under faults in motor windings and converter switches. The drive system of a conventional multi-phase motor is usually based on an inverter connected to a direct current (DC) source. This system has drawbacks, including dependency on single DC link and physical/electrical connection between motor phases. In addition, a modular-phase system requires multiple isolated DC sources and multiple full-bridge inverters, which results in a very expensive, complex, and bulky system.
Symmetrical multi-fed drives based on three-phase modules are of special interest in safety critical applications. They offer simple control under a fault condition. However, even a single open-circuit fault of one switch or winding will cause complete interruption of a faulty module. Furthermore, straightforward extension of a symmetrical multi-fed drive concept into multi-phase motors will result in a drive with a high component count. For example, a symmetrical two-fed drive based on two five-phase, five-leg bridges requires 20 switches.